From Tomber's Wobbling Guide:
http://smashboards.com/threads/behind-wobbling-all-the-stuff-you-dont-see.340028/#post-15790583
On that note, to me it seems like f-tilt wobble is superior to d-tilt in almost every way. More damage (fewer reps), more hitlag (locks longer so more room for error), comes out faster (easier to get started faster from grab), and IASA is 1 frame sooner (closer to grab attack's duration). D-tilt has slightly more horizontal range though.
*F-tilt is always superior to d-tilt unless you’re
- Standing very close to an edge
- Trying to time out your opponent. It takes more time to get to 300% using d-tilt than using f-tilt
- Playing on Dream Land while you’re not facing the tree. The wind can screw you over if you’re using f-tilt near an edge
Sometimes I shift between f-tilt and d-tilt when I’m wobbling. It looks cool and it’s a good thing to be able to do. I often find myself in a situation where I’m wobbling someone using f-tilt on Dream Land when suddenly the wind blows me to the edge. In situations like this I do a few f-tilt and then shift to d-tilt midway in the wobbling before I reach the end of the stage/platform I’m standing on.